In asphalt pavement and concrete pavement, cracks are inevitable and caused by: reflective cracking, thermal cracking, and fatigue cracking. Cracks allow easy access for water to reach the base, sub-base, or subgrade. Water can deteriorate the substructure and shorten the life of pavement substantially. When cracking has occurred, sealants are typically applied. A goal when applying sealants is to prevent water from seeping through the crack, and to prevent the entry of substances such as salt that might further decay base material and enlarge the crack.
Unfortunately however, current pavement sealants commonly suffer from “adhesion loss.” When adhesion loss occurs, one or more surfaces of the sealant pull away from the crack, and consequently a crack reappears. Such separation may occur in colder seasons such as upon freezing or rapid temperature changes, and may also occur in warmer months upon a sudden temperature drop such as from hail storms or rain downpours. This is because of the different thermal expansion properties of the sealant and the concrete/asphalt, and because the strength of sealant, its adhesive strength and/or ductility is not large enough. In addition, during warmer months the structural material which has been repaired undergoes thermal expansion, as does the sealant itself, and this tends to squeeze sealant out of the repaired area.
Similarly, expansion joints are weak links in bridge decks or concrete pavement. Expansion joint failure is a leading cause for structural damage to bridge superstructures or concrete pavement. Due to the critical role played by joints in bridge decks and pavements, crack or joint sealants have been a topic of intensive research for many years.
Various types of sealants have been utilized to seal expansion joints in bridge decks and pavements. The most frequently used types of sealed joints include, but are not limited to, (1) field-poured silicone and polymer modified asphalt joints; (2) compression seal joints; (3) strip seal joints; (4) polymer modified asphalt plug joint system; (5) inflatable neoprene joints; and (6) modular joint sealing system. However, two fundamental problems continue to be challenges in the scientific and industrial community: (1) the gradually loss of interfacial contact, due to plastic deformation of sealant materials, and (2) sealant squeezing out of the channel in summer due to Poisson's ratio effect and thermal expansion.
Thus, there continues to be a need for structural sealants that are resistant to adhesion loss. Moreover, there is also a need for sealants which resist being expelled from repaired defect (or expansion joint) during thermal expansion of the repaired structure. In particular, the need also continues for sealants that are both resistant to adhesion loss, and resistant to being expelled at warmer temperatures.